Test fixture and method of liquid leak testing an electronic device

Abstract

A method and apparatus to ensure proper operation of an air permeable vent on an electronic device by allowing the vent and its surrounding area to be pressure decay leak tested using liquid to create the seal around the air permeable vent. The method may include filling a chamber with a known volume of liquid to cover the vent. Then, a remaining volume of air can be pressurized and monitored to detect a liquid leak either through the vent or through the sealing surface around or between the vent and the substrate of the electronic device. A pressure decay unit may adequately determine a leak rate to determine if the electronic device will pass or fail the required IP rating.

What is claimed is: 
     
       1. A method for liquid leak testing of an air permeable vent of a test unit, wherein the test unit is an electronic device that contains the air permeable vent or a portion of the electronic device that contains the air permeable vent, comprising:
 opening a test fixture; 
 inserting the test unit into a first member of the test fixture, wherein the first member of the test fixture includes a chamber, a passage extending from a first opening of the chamber to a second opening on an engaging surface, and a seal that surrounds the second opening of the passage and is configured to contact a sealing region on a first side of the test unit, wherein the sealing region includes the air permeable vent and a portion of an adjacent surface around the air permeable vent; 
 arranging a second member of the test fixture on a second side of the test unit; 
 engaging the seal to the adjacent surface around the air permeable vent creating the sealing region; 
 filling the passage and a first portion of the chamber with a predetermined volume of a liquid, wherein the liquid completely fills the passage such that the liquid completely covers the sealing region; 
 filling a second portion of the chamber with air to a predetermined air pressure; 
 measuring air pressure in the chamber over a predetermined time to determine a measured air pressure decay; and 
 comparing the measured air pressure decay to a predetermined air pressure decay, wherein if the measured air pressure decay is greater than the predetermined air pressure decay, the test unit fails, and if the measured air pressure decay is less than the predetermined air pressure decay, the test unit passes. 
 
     
     
       2. The method of  claim 1 , wherein the liquid is water. 
     
     
       3. The method of  claim 2 , wherein the predetermined air pressure in the chamber is 1.4 psi. 
     
     
       4. The method of  claim 1 , wherein the seal is an O-ring, wherein the O-ring only contacts the adjacent surface around the air permeable vent on the first side of the test unit. 
     
     
       5. The method of  claim 1 , wherein when the measured air pressure decay is measured with a differential air pressure decay unit, the predetermined time is within a range of 120 seconds and 240 seconds. 
     
     
       6. The method of  claim 1 , wherein the first member of the test fixture includes a liquid inlet that allows the liquid to flow into the chamber and a liquid drain that allows the liquid to flow out of the chamber. 
     
     
       7. The method of  claim 1 , wherein the first member of the test fixture includes an air pressurizer port that allows the air in the chamber to be pressurized. 
     
     
       8. The method of  claim 1 , wherein the portion of the adjacent surface around the air permeable vent extends at least 2 mm outward of the air permeable vent in every direction along the first side. 
     
     
       9. The method of  claim 1 , wherein the passage extends from a rear surface of the chamber toward the engaging surface. 
     
     
       10. The method of  claim 1 , wherein the passage has a first perimeter that is within a range of 1 percent and 15 percent greater than a second perimeter of the air permeable vent. 
     
     
       11. The method of  claim 1 , wherein the passage has a generally cylindrical shape. 
     
     
       12. A method for liquid leak testing of an air permeable vent of a test unit, wherein the test unit is an electronic device that contains the air permeable vent or a portion of the electronic device that contains the air permeable vent, comprising:
 opening a test fixture; 
 inserting the test unit into a first member of the test fixture, wherein the first member of the test fixture includes a chamber and a seal, wherein the seal is configured to contact a sealing region on a first side of the test unit and the sealing region includes the air permeable vent and a portion of an adjacent surface around the air permeable vent; 
 arranging a second member of the test fixture on a second side of the test unit; 
 engaging the seal to the adjacent surface around the air permeable vent creating the sealing region; 
 filling a first portion of the chamber with a predetermined volume of a liquid, wherein the liquid completely covers the sealing region; 
 filling a second portion of the chamber with a predetermined volume of air to a predetermined air pressure; 
 measuring air pressure in the chamber over a predetermined time to determine a measured air pressure decay; and 
 comparing the measured air pressure decay to a predetermined air pressure decay, wherein if the measured air pressure decay is greater than the predetermined air pressure decay, the test unit fails, and if the measured air pressure decay is less than the predetermined air pressure decay, the test unit passes. 
 
     
     
       13. The method of  claim 12 , wherein the liquid is water. 
     
     
       14. The method of  claim 12 , wherein the first member of the test fixture includes a liquid inlet that allows the liquid to flow into the chamber and a liquid drain that allows the liquid to flow out of the chamber. 
     
     
       15. The method of  claim 12 , wherein the first member of the test fixture includes an air pressurizer port that allows the air in the chamber to be pressurized. 
     
     
       16. The method of  claim 12 , wherein the first member of the test fixture further includes a passage that extends from a rear surface of the chamber towards the sealing region on the test unit. 
     
     
       17. The method of  claim 16 , wherein the passage has a first perimeter that is within a range of 1 percent and 15 percent greater than a second perimeter of the air permeable vent. 
     
     
       18. A method for water leak testing of an air permeable vent of a test unit, wherein the test unit is an electronic device that contains the air permeable vent or a portion of the electronic device that contains the air permeable vent, comprising:
 opening a test fixture; 
 inserting the test unit into a first member of the test fixture; wherein the first member of the test fixture includes a chamber, a passage extending from a first opening of the chamber to a second opening on an engaging surface, and a seal that surrounds the second opening of the passage and is configured to contact a sealing region on a first side of the test unit, wherein the sealing region includes the air permeable vent and a portion of an adjacent surface around the air permeable vent, wherein the passage has a first perimeter that is within a range of 1 percent and 15 percent greater than a second perimeter of the air permeable vent, and the engaging surface faces the first side of the test unit; 
 arranging a second member of the test fixture on a second side of the test unit; 
 engaging the seal to the adjacent surface around the air permeable vent creating the sealing region; 
 filling the passage and a first portion of the chamber with a predetermined volume of water, wherein the water completely fills the passage such that the water completely covers the sealing region; 
 filling a second portion of the chamber with a predetermined volume of air to a predetermined air pressure; 
 measuring air pressure in the chamber over a predetermined time to determine a measured air pressure decay; and 
 comparing the measured air pressure decay to a predetermined air pressure decay, wherein if the measured air pressure decay is greater than the predetermined air pressure decay, the test unit fails, and if the measured air pressure decay is less than the predetermined air pressure decay, the test unit passes. 
 
     
     
       19. The method of  claim 18 , wherein the portion of the adjacent surface around the air permeable vent extends at least 2 mm outward of the air permeable vent in every direction along the first side. 
     
     
       20. The method of  claim 18 , wherein the passage extends from a rear surface of the chamber toward the engaging surface.